1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, copier, facsimile, etc. and more particularly to an image forming apparatus which can easily remove a jammed sheet of paper (hereinafter referred to as "jammed sheet") at a sheet feeding unit where a paper jam is likely to occur and can minimize a space necessary for maintenance such as removal of a jammed sheet.
2. Description of the Related Art
FIG. 1 is a conceptual sectional view showing a main part of a conventional image forming apparatus 1 such as a printer, copier, facsimile, etc., particularly having a sheet feeding device 2 with a removable tray accommodating sheets therein.
In the sheet feeding device 2 of such a conventional image forming apparatus 1, sheets P and Q stacked on cassette plates (not shown) within trays 3 and 4 arranged at upper and lower stages are urged upward by springs arranged on the lower sides of the trays plates respectively so that they are forced into contact with sheet feeding roles 5 and 6 each having a sectional crescent shape, respectively.
The sheet P arranged within the trays 3 at the upper stage is pulled out from the trays 3 in accordance with the rotation of the sheet feeding roll 5, is guided along a chute 7 as indicated by arrow A and transported to an image forming unit 9 of an electrostatic recording type including a photoreceptor drum 8.
Incidentally, the trays 3 and 4 are accommodated within supporting boxes 10 and 11, respectively. At the time of maintenance/inspection such as filling of sheets of paper P and Q, these trays 3 and 4 can be pulled out from the supporting boxes 10 and 11, respectively, in a direction perpendicular to the paper face of the drawing.
Such a sheet feeding device 2 is disclosed in e.g. Japanese Utility Model Unexamined Publication No. Hei. 4-70836.
In the sheet feeding device 2, a sheet guiding passage 13 is formed between the shute 7 and a wall 12 constituting a part of a box-shaped apparatus body.
The sheet Q pulled out from the tray 4 at the lower stage by the sheet feeding roll 6 is transported upward to the image forming unit 9 as indicated by arrow B through a chute 14 and the passage 13.
In the conventional image forming apparatus 1, when a sheet Q is jammed in the sheet guiding passage 13, i.e. when a paper jam occurs, the sheet feeding tray 4 at the lower stage is detached from the supporting box 11 to remove the sheet Q. In this case, the chute 14 and sheet feeding roll 6 hinders an operator's hand from reaching the jammed sheet. This makes it difficult to remove the sheet Q having caused the paper jam from the passage 13.
This problem can be solved by an image forming apparatus disclosed in Japanese Patent Unexamined Publication No. Hei. 4-256642.
In the image forming apparatus disclosed in Japanese Patent Unexamined Publication No. Hei. 4-256642, another chute which constitutes a sheet guiding passage in cooperation with a member corresponding to the above chute 14, i.e. a portion corresponding to the wall 12 in FIG. 1 is tilted toward the rear side of the sheet feeding device 2 as indicated by arrow C to open the passage 13.
Therefore, when a paper jam occurs, by opening the chute (i.e. portion corresponding to the wall 12 in FIG. 1), the jammed sheet can be easily removed.
However, the conventional image forming apparatus in which the one chute constituting the sheet guiding passage is movable has still the following problem.
Generally, for easy attaching/detaching, the tray is attached from the front of the body of the image forming apparatus while the movable chute for opening the sheet guiding passage is arranged on the rear side of the image forming apparatus.
In this case, at the time of maintenance/inspection such as removal of a paper jam, in order that the movable chute can be tilted, a space enough to tilt the chute must be assured on the rear side of the image forming apparatus. In addition, a further space must be preferably assured so that an operator can enter the rear side to work facing the rear of the image forming apparatus.
Thus, each of the conventional image forming apparatus has a disadvantage that the space which is not generally required must be assured around the image forming apparatus in preparation against abnormality such as occurrence of a paper jam.
In recent years, the image forming apparatus such as a printer is required to have a performance of downsizing, i.e. promotion of space saving as well as miniaturizing. From such a point of view, it may be out of the question that the conventional image forming apparatus described above requires the space on the rear side of the apparatus for the purpose of removing the paper jam.
As a result, each of the conventional image forming apparatus as described above can realize miniaturizing of its own size, but cannot still reduce the space necessary for its installation from the viewpoint of assuring the space necessary for maintenance/inspection such as removal of a paper jam.